The use of a flow control device utilizing a resilient compressible member preferably shaped in the form of a disc or the like having at least one orifice therethrough that is able to constrict and expand in response to compression and relaxation of the member against a seat in a passageway in response to respective increases and decreases in the fluid pressure differential across the member to maintain a substantially constant rate of fluid flow through the passageway are well known in the art.
One of the problems heretofore associated with such flow control devices has been noise and flutter associated with oscillation of the resilient member under varying fluid pressure differentials across the member particularly where high fluid pressure differentials are involved. As a means of increasing flow at low pressure, it has been common practice in the past to include pads interspersed by bypass channels about the periphery of the downstream side of the resilient member through and around which the fluid is able to flow at least at lower fluid pressure differentials across the member but which can be controlled to the point where they become sealed by compression of the pads against the seat as higher fluid pressure differentials are imposed across the member.
An example of such a flow control device in which the compressible member features a combination of a single orifice and a symmetrical array of bypass channels about its periphery is disclosed in U.S. Pat. No. 2,936,790, the disclosure of which is incorporated herein by reference. The device, however, utilizes a symmetrical arrangement of resilient pads that are adapted to engage the seat and establish a predetermined spaced relationship therefrom at a desired fluid pressure differential across the member so that the fluid can flow through the bypass channels and inwardly across the seat and into the downstream side of the passageway until the fluid pressure differential across the member is increased to a point at which the pads become compressed sufficiently to enable the surface of the compressible member from which they extend to press against the seat and seal the flow. These pads increase the all-over dimensions of the flow control member resulting in larger space requirements for their application.
An example of a fluid flow control device utilizing a resilient compressible member having a plurality of orifices to reduce noise that are able to constrict and expand to maintain a substantially constant rate of fluid flow through a passageway but which does not have pads or bypass channels is disclosed in U.S. Pat. No. 3,006,378, the disclosure of which is incorporated herein by reference. Although such compressible member may be used to advantage in controlling flow rate of the fluid, the absence of bypass flow channels results in low flow at low pressures.
Consequently, the prior art fluid control devices utilizing bypass channels in combination with pads on their downstream side have resulted in an increase of resiliency of the flow control member which under certain conditions of flow and pressure will cause flutter or rapid oscillation of the center part of the fluid control member causing fatigue failure leading to their ultimate break up.
In view of the above, a need exists to provide a fatigue resistant flow control device utilizing a resilient compressible member having at least one orifice therethrough that is able to contract and expand upon compression and relaxation of the member against a seat in a passageway to maintain a substantially constant rate of flow through the passageway in response to respective increases and decreases in the fluid pressure differential across the member in addition to having fluid bypass channels as a means of increasing flow at lower fluid pressures.